Hepsin is a novel serine protease of the trypsin family and contains a transmembrane domain near its amino-terminus. The structural feature distinguishes hepsin from most other serine proteases. Biochemical studies indicate that hepsin is a type II transmembrane serine protease expressed mainly on the surface of hepatocytes. Hepsin has an extra-cellular proteolytic domain and exhibits low sequence homology to other known proteases. Lower levels of hepsin mRNA are detected in other tissues including lung, kidney, pancreas, stomach, thyroid and prostate. In addition, hepsin mRNA is present in several human tumor cell lines, such as hepatoma cells HepG2 and PLC/PRF/5, mammary cancer cells MCF784 and T470, and epitheloid carcinoma cells HeLa S3 (Torres-Rosado, A. et al., Proc. Natl. Acad. Sci. USA 1993;90:7181–7185). Further in vitro studies have shown inhibition of hepatoma cell proliferation using hepsin inhibitors (Torres-Rosado, A. et al. Proc. Natl. Acad. Sci. USA 1993;90:7181–7185). Recently, hepsin overexpression was observed in prostate, breast, kidney and ovarian cancers and due to low homology to other known proteases, it may provide a unique target for pharmacological or interventional therapy.
U.S. Pat. No. 5,981,830 issued on Nov. 9, 1999, entire contents of which are incorporated herein by reference, discloses nucleotide and amino acid hepsin sequence. The U.S. Pat. No. 5,981,830 patent further discloses a transgenic mouse comprising a disrupted hepsin gene and methods of making the transgenic mouse comprising the disrupted hepsin gene by utilizing a hepsin targeting vector for homologous recombination in mouse embryonic stem cells.
Hepsin is necessary for cell growth in vitro and may play a role in metastatic expansion by factor VII (a blood coagulation factor) activation, thereby initiating a coagulation pathway on the cell surface that leads to thrombin formation (Kazama et al., J. Biol. Chem. 1995;270:66–72). The observed molecular mass of hepsin by immunoblotting is 45.3 kDa. Cloning and characterization of the mouse and rat hepsin indicate 88% overall homology with human hepsin.
More recently, a connection between the role of hepsin in coagulation and the neoplastic phenotype was suggested. It was demonstrated that hepsin is highly expressed in renal cell carcinoma, and from these results it was proposed that hepsin might be the initiator of tumor cell-induced thrombin generation in certain tumors that lack tissue factor expression (Zacharski et al., Thromb. Haemost., 1998;79:876–877).
Several in vitro studies have suggested that hepsin may play a role in blood coagulation, hepatocyte growth, and fertilization. To determine the functional importance of hepsin, hepsin-deficient mice were generated by homologous recombination. Homozygous hepsin-deficient mice were viable and fertile, and grew normally. When analyzed in hemostasis assays, such as tail bleeding time and plasma clotting times, and in vivo modes, such as disseminated intravascular coagulation, septic shock, and acute liver regeneration, hepsin-deficient mice had similar phenotypes as wild-type controls. Liver weight and serum concentrations of liver-derived proteins or enzymes were also similar in hepsin-deficient and wild-type mice. No abnormalities were identified in major organs in hepsin-deficient mice in histological examinations. These results indicate that hepsin is not an essential enzyme for normal hemostasis, embryogenesis, and maintenance of normal liver function. Unexpectedly, serum concentrations of bone-derived alkaline phosphatase were approximately two-fold higher in both male and female hepsin-deficient mice than those in wild-type controls. The underlying mechanism for this phenotype and long-term effects of hepsin deficiency remain to be determined.
Hepsin might be involved in the development of prostate cancer. If a target drug were to be developed to inhibit hepsin, it appears that this drug would have the potential to be effective for a majority of prostate cancer patients. And since hepsin appears to be excessively produced in most prostate cancers, chemicals that block the actions of hepsin could possibly prevent prostate cancer from developing or progressing. It is one aspect of the present invention to provide a method for treating prostate cancer of a patient comprising administering a hepsin antagonist with a dosage effective to suppress or inactivate hepsin's expression, particularly site specifically at the target tissue by local administration. A dosage of hepsin antagonist herein may consist one dose or multiple doses administered over time.
Prostate cancer is the most commonly diagnosed noncutaneous cancer in men. Despite this fact, many of the genetic changes that coincide with prostate cancer progression remain enigmatic. The expression profiles of several benign and malignant human prostate samples have been characterized and identified with several genes that are differentially expressed between benign and malignant glands. One gene that was overexpressed encodes the serine protease hepsin. In situ hybridization demonstrates that hepsin is specifically overexpressed in the carcinoma cells themselves. These facts, together with the molecular properties of hepsin, make it an ideal target for prostate cancer therapy (Magee J A, et al. Cancer Research 2001;61(15):5692–5696)